security: Reorganizing source code to prepare for support of two version of NDN certificates

This commit also removes unused ndn_digestSha256 function and deprecates
crypto::sha256 in favor of crypto::computeSha256Digest in util/crypto.hpp.

Change-Id: I24ee50ff073a96b868633bdf2cfade412d3605f3
Refs: #3098
diff --git a/src/face.hpp b/src/face.hpp
index 51a5270..27af415 100644
--- a/src/face.hpp
+++ b/src/face.hpp
@@ -35,7 +35,7 @@
 #define NDN_FACE_KEEP_DEPRECATED_REGISTRATION_SIGNING
 
 #ifdef NDN_FACE_KEEP_DEPRECATED_REGISTRATION_SIGNING
-#include "security/identity-certificate.hpp"
+#include "security/v1/identity-certificate.hpp"
 #endif // NDN_FACE_KEEP_DEPRECATED_REGISTRATION_SIGNING
 
 namespace boost {
@@ -414,7 +414,7 @@
                     const OnInterest& onInterest,
                     const RegisterPrefixSuccessCallback& onSuccess,
                     const RegisterPrefixFailureCallback& onFailure,
-                    const IdentityCertificate& certificate,
+                    const security::v1::IdentityCertificate& certificate,
                     uint64_t flags = nfd::ROUTE_FLAG_CHILD_INHERIT));
 
   /**
@@ -444,7 +444,7 @@
   setInterestFilter(const InterestFilter& interestFilter,
                     const OnInterest& onInterest,
                     const RegisterPrefixFailureCallback& onFailure,
-                    const IdentityCertificate& certificate,
+                    const security::v1::IdentityCertificate& certificate,
                     uint64_t flags = nfd::ROUTE_FLAG_CHILD_INHERIT));
 
   /**
@@ -554,7 +554,7 @@
   registerPrefix(const Name& prefix,
                  const RegisterPrefixSuccessCallback& onSuccess,
                  const RegisterPrefixFailureCallback& onFailure,
-                 const IdentityCertificate& certificate,
+                 const security::v1::IdentityCertificate& certificate,
                  uint64_t flags = nfd::ROUTE_FLAG_CHILD_INHERIT));
 
   /**